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(No Model.) 2 Sheets-Sheet 1.

. 'P. R. COLVIN. I SYSTEM or TELEPHONIG .INTERGOMMUNIGATION. No. 504,103. Patented Aug. 29, 18 93.

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' P. R. OOLVIN.

' SYSTEM OF TELEPHONIG INTERGOMMUNIGATION.

Patented Aug. 29,1893.

' %.s&em. I 3513 M attozuemv I wvemboz UNITED STATES PATENT OFFICE.

FRANK R. ooLvIN, on NEW YORK, N. Y.

SYSTEM OF TELEPHONIC INTERCOMMUNICATION.

SPECIFICATION forming part of Letters Patent No. 504,103, dated August 29, 1893. Application filed February 6, 1893. Serial No. 461,159- (No model.)

To all whom it may concern.-

3e it known that I, FRANK R. COLVIN, a OltlZQIl of the United States, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Systems of Telephonic Intercommunicatlon, of which the following is a specification.

My present invention relates to a system of telephonic intercommunication between a plurality of stations, in which provision is made whereby each station may at will place itself in direct communication with any desired one of the other stations in the system, and to this end it comprises certain improvements in the apparatus and methods described in my prior application for Letters-Patent of the United States, filed October 15, 1892, Serial No. 448,958.

In the accompanying drawings, which represent a system of telephonic intercommunicatlon embodying my invention, Figure 1 shows such a system in its most elementary form, having two stations only in connection. Fig. 2 illustrates a modification in the arrangement of the connections. Fig. 3 is an elevation of the signaling apparatus. Fig. lillustrates a multiple keyboard, and Fig. 5 is a perspective view of a multiple signaling apparatus.

Referring first to Fig. l, L is the line connecting two terminal stations respectively designated as station A and station B. As the apparatus at each station is a duplicate of that of the other, it will suffice to describe I in the first instance, the apparatus of station A only. Entering the station at A, the line L first passes through a pair of three-point keys K and K (the function of which will be hereinafter explained), from whence the circuit is continued by the branch line L to the electromagnet of the visual signal V. This signal is preferably of the type known as an electric drop-shutter. Its electromagnet, when energized by the passage of the current, releases a shutter '0 which drops by gravity into a position (shown in dotted lines) to display an arbitrary designating character or numeral. This shutter carries an electrical contact at, which, when the shutter has fallen, touches the stop w and thus closes a shunt circuit to, which operates to divert the current from the'coils of the electromagnet by is likewise permanently connected with the ground or return at G, isa telephone T. This branch is normally open, and bifurcates into two sub-branches Z and Z both of which are normally open,and terminate respectively at the working contacts of the keys K and K One of these sub-branches Z contains a battery or other equivalent source of electricity E. The keys K and K are of the threepoint type, in which the lever is normally held by a spring against a resting-contact, but may be depressed by the pressure of the finger upon an insulating knob 01' button, so as to remove it from the resting contact and place it upon the working contact. In practice it is preferably constructed in the form of an ordinary press-button.

The telephone T may be included in the second or normally open branch, at any point between the working contact of key K and the earth at G. It is preferable to include it in the undivided portion of this circuit, as shown in Fig. 1, but it may in some cases be placed in the sub-branch Z as shown in Fig. 2.

It is desirable that the telephone T when placed in the undivided portion of the circuit or branch L should be provided with an attachment whereby it is automatically shunted or out out of the circuit when not in use. I have shown a convenient and. eifective device for this purpose in which one of the terminals of the telephone is provided with a metallic hook t, which may be inserted into the stationary eye g for suspending the telephone when not in use. This eye g is in electrical connection with the opposite terminal 15 of the telephone T, and hence when it is hung up, as shown at station A in Fig. 1, the contact of the metallic hook and eye forms a short circuit or shunt, and diverts the current of the line from the telephone. When the telephone is removed from the hook, as shown at ICO station B in Fig. l,the current at once passes freely through the instrument;

The mode of operation of the apparatus is as follows: Referring first to Fig. 1, if for example a person at station A wishes to converse with a person at station B, he depresses the key or press-button K and then removes the telephone T from its place of suspension and applies it to his ear. The depression of the key K causes a current to flow from the battery E through the line L and thence through the resting contacts of the keys is and k at station E, actuating the drop shutter V at the distant station B, which falls down, removing the resistance of its own electromagnet coil from the line, and thus strengthening the current so that it is able to actuate the call apparatus 0. The person at station B, hearing the call, and furthermore observing by the indication of the shutter from which line the call has proceeded (especially in case there may be more than one line), depresses his key 10 removes his telephone from its point of suspension, and thus places his apparatus in circuit for conversation. The person calling at station A now continues to depress key K by which operation all the apparatus is removed from the line except the two telephones and the battery E at station A. Both keys, K and k are kept depressed so long as the conversation continues, and when it is completed, their simultaneous release restores the line and apparatus to their normal positions.

In the organization shown in Fig. 1, it is quite immaterial Whether a single telephone T isemployed both for speaking or hearing,

or whether aseparate transmitter and receiver are used. The last named arrangement will in most cases be found more convenient than the other. When there are more than two stations in the system, as will usually be the case, a shutter and two keys will be required at each station for each separate line of com- In the practical construction of the apparatus, it is advisable to make the knob of the key or press-button K, which is-used while calling and speaking, of a diiferent color from E K which is employed for answering, as this 1 serves to render them more easily distinl guishable. I prefer to use black for the calling and white for the answering key.

When two or more keys are required to be I used the convenient and cheap style of conso4,1( a

struction shown in Fig. 4 may be employed with advantage. The poles of the battery are electrically connected with the metallic bars B B which extend along the whole range of keys. The keys K and K are pressed forward from behind by means of the button S (shown in dottedlines), and are thus brought into contact with one or the other of the bars, the connections being formed precisely as in Fi 1.

l ig. 5 shows the external appearance of the signaling apparatus, the press-buttons of the respective keys being at the top and the drop shutters c u v in front of the box or case. It will be understood that any required number of these may be used corresponding to the different number of lines of communication.

I claim as my invention 1. In a telephonic system, two branches at each station; a signaling apparatus included in the first branch; two sub-branches constituting the terminals of the second branch, and a source of electricity included in one of said sub-branches; in combination with two three-point keys at each station, the first key having its lever connected to the line, its working contact to the sub-branch whlch includes the source of electricity, and its testing contact to the lever of the secondkey; the second key having its resting contact con nected to the branch including the signaling apparatus, and its working contact to the remaining sub-branch, and a telephone included in the second branch at a point between the working contact of the second key and the ground or return circuit. 7 p

2. In a telephone system the combination of the main circuit and a portable telephone having one of its terminals provided with a metallic extension mounted on the instrument, and the other in electrical connection with a metallic support upon which thetelephone may be hung, the two terminals leading to opposite sides of the circuit, whereby, when the telephone rests on the support,- it is short-circuited, but when removed therefrom the short-circuit is open.

3. In a telephone system, a branch perm-a nently connected with the ground or return at each station and terminating in two normally open sub-branches; a telephone included in the undivided portion of said branch, a source of electricity included in one of said subbranches, and two independent keys whereby either of said branches may be connected with the main line at will.

4. In a signaling system, the bars B B, in combination with two or more pairs of keys, the individual keys of each pair being normally in connection with each other, but making contact, when separately depressed, with the respective bars.

5. In a signaling system, the bars B Bone connected through a battery and the other through a speaking instrument, with a common earth or return circuit, and two or more pairs of keys, the individual keys of each too IO mally in connection with each other, but making contact, when separately depressed, with the respective bars.

In testimony whereof I have hereunto subscribed my name this 4th day of February, A. D. 1893.

FRANK R. OOLVIN.

Witnesses:

T. COMMERFORD MARTIN, W. RICHARD HUTCHINS. 

